Thewritingofthisbookhasbeeninspiredbytheexperienceofteachinga courseonDetectionandSignalProcessingtograduatestudentsoveraperiod ofmanyyears. Itwasstrikingthatstudentswerenotonlyfascinatedbythe variousdetectionprinciplesandtechnicalperformancesofpracticalsystems, butalsobytheprofessionalismoftheinvolved typical physicalengine- ing. Usuallystudentsarethoroughlytaughtindi'erentcoursesofphysics, whicharemostlystudiedasisolated'elds. Thecourseondetectionands- nalprocessingisbasedontypicalresultsthatwereestablishedindi'erent disciplines like optics, solid state physics, thermodynamics, mathematical statistics, Fouriertransforms, andelectroniccircuitry. Theirsimultaneousand interdependentapplicationbroadenstheinsightofmutualrelationsinthev- ious'elds. Forinstancethe'uctuationsofthermalbackgroundradiationcan bederivedeitherwiththeblackbodytheoryorindependentlywithther- dynamicstoarriveatthesameresult. AlsotheappliedFourierrelationsin thefrequencyandtimedomainsarenolongerabstractmathematicalman- ulationsbutpracticaltoolsandprobablyeasiertounderstandintheapplied technique. Estimatesoftheorderofmagnitudeswithcomparisonofrelevant physicale'ectsnecessarybydesigningadeviceareveryinstructive. Ingeneral theachievementsofvariousdisciplinesarebroughttogethertodesignandto evaluatequantitativelythetechnicalperformancesofdetectiontechniques. Thustheinterestfordetectionandsignalprocessingisbothtolearnthe knowledgefordesigningpracticaldetectionsystemsandtogetacquainted withthethinkingofphysicalengineering. The'rstpartofthebookisdevotedtonoisephenomenaandradiation detectors. Fundamentaldescriptionswithquantitativeanalysesoftheund- lyingphysicalprocessesofbothdetectorsandaccompanyingnoiseleadto understandthepotentialswithrespecttosensitivityandoperatingfrequency domain. Thesecondpartdealswithampli'cationproblemsandtherecovery ofrepetitivesignalsburiedinnoise. Thelastpartisdevotedtosolvingthe problemsconnectedwithreachingtheultimatedetectionlimitorquantum limit. Thisisdoneforheterodynedetectionandphotoncounting. Although VIII Preface heterodynedetectionyieldstheultimatesensitivity, itsspatialmodesel- tivityand, ingeneral, thelowspectralpowerdensityofthesignalrequire sophisticatedprovisions. Thisisdiscussedindetail. Theinherentproblemsare analyzedandappropriatetechnicalsolutionsaredescribedtoreachtheul- matesensitivityfordetectingincoherentradiationandcommunicationsignals thatarerandomlyDopplershifted. Theresultsareillustratedwithexamples ofspacecommunication. Hengelo(O), January2006 W. J. Witteman Contents 1 RandomFluctuations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 2 ThermalNoiseofResistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. 3 ShotNoise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. 3. 1 SpectralDistribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 3. 2 Photons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. 4 FlickerNoise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. 5 Generation-RecombinationNoise. . . . . . . . . . . . . . . . . . . . . . . . . . 10 1. 6 ThermalRadiationandItsFluctuations. . . . . . . . . . . . . . . . . . . . 13 1. 7 TemperatureFluctuationsofSmallBodies. . . . . . . . . . . . . . . . . . 18 1. 7. 1 AbsorptionandEmissionFluctuations. . . .